A355483 a(1) = 1; for n > 1, a(n) is the smallest positive number that has not yet appeared such that the number of 1-bits in the binary expansion of a(n) equals the number of divisors of a(n-1).
1, 2, 3, 5, 6, 15, 23, 9, 7, 10, 27, 29, 12, 63, 95, 30, 255, 383, 17, 18, 111, 39, 43, 20, 119, 45, 123, 46, 51, 53, 24, 447, 54, 479, 33, 57, 58, 60, 4095, 16777215, 79228162514264337593543950335
Offset: 1
Examples
a(7) = 23 = 10111_2 as a(6) = 15 which has four divisors, and 23 is the smallest unused number that has four 1-bits in its binary expansion.
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